Subsequent Events Subsequent Events (Details Textual) - USD ($)		3 Months Ended								12 Months Ended
	Feb. 03, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 29, 2020	Feb. 28, 2019	Feb. 14, 2018	Nov. 15, 2017	Oct. 17, 2016
Subsequent Event [Line Items]
Stock Repurchase Program, Authorized Amount														$ 225,000,000	$ 350,000,000	$ 150,000,000	$ 400,000,000
Dividends declared per share (usd per share)		$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.50	$ 2.40	$ 2.30	$ 2.00
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock Repurchase Program, Authorized Amount													$ 200,000,000
Dividend Declared [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends declared per share (usd per share)	$ 0.60